Heart and Stroke Encyclopedia

Knowledge starts here.

Hands-Only? CPR focuses on providing chest compressions, not rescue breaths. Hands-Only CPR is recommended for an adult who suddenly collapses outside the hospital. If someone collapses: (1) Call 9-1-1; and (2) Pump hard and fast in the center of the chest at the rate of at least 100 compressions per minute. You may dramatically increase the victim's survival chances. You can sing "Stayin' Alive" to help you keep the right beat.

An HbA1c test, which is also called hemoglobin A1C, measures a person's average blood glucose level over two or three months. It is used to screen for diabetes and to monitor how well the condition is being managed.

High-density lipoprotein cholesterol is known as "good" cholesterol because high levels of HDL seem to protect against heart attacks. Low levels of HDL seem to increase the risk of heart disease. Medical experts think HDL tends to carry cholesterol away from the arteries and back to the liver, where it's passed from the body. Some experts believe HDL removes excess cholesterol from arterial plaque, slowing its buildup.

A heart/lung machine is used during heart surgery to keep blood pumping through a patient's body. It's used during many types of open-chest surgeries in which blood is diverted from the heart and lungs through a heart/lung machine and oxygenated blood is returned to the aorta.

A heart attack occurs when a blocked coronary artery prevents oxygen-rich blood from reaching a section of the heart muscle. If the blocked artery is not reopened quickly, the part of the heart normally nourished by that artery begins to die. Symptoms can come on suddenly but may start slowly and persist over time . Warning signs include discomfort in the chest (pressure, squeezing, fullness), discomfort in other upper-body areas (arms, back, neck, jaw or stomach), shortness of breath, a cold sweat, nausea or lightheadedness. As with men, women's most common heart attack symptom is chest pain or discomfort. But women are somewhat more likely than men to experience some of the other common symptoms, particularly shortness of breath, nausea, vomiting and back or jaw pain. Call 9-1-1 if you think you or someone else is having a heart attack.

A heart attack blood test can confirm or refute suspicions that a person has suffered a heart attack. These tests can detect abnormal levels of certain enzymes released into the bloodstream when heart muscle cells die.

Some heart attacks are sudden and intense but most start slowly, with mild pain or discomfort. Here are signs that can mean a heart attack is happening:

Chest discomfort. Most heart attacks involve discomfort in the center of the chest that lasts more than a few minutes, or that goes away and comes back. It can feel like uncomfortable pressure, squeezing, fullness or pain.

Discomfort in other areas of the upper body. Symptoms can include pain or discomfort in one or both arms, the back, neck, jaw or stomach.

Shortness of breath with or without chest discomfort.

Other signs may include breaking out in a cold sweat, nausea or lightheadedness.

If you've had a heart attack, you will most likely take medications for the rest of your life. There are many types and combinations of drugs used to help prevent having another heart attack. You and your doctor need to discuss the best treatment for you. You may receive one of the following types of medication:

Signs of a heart attack include discomfort in the chest (pressure, squeezing, fullness), discomfort in other upper-body areas (arms, back, neck, jaw or stomach), shortness of breath, a cold sweat, nausea or lightheadedness. As with men, women's most common heart attack symptom is chest pain or discomfort. But women are somewhat more likely than men to experience some of the other common symptoms, particularly shortness of breath, nausea, vomiting and back or jaw pain. Call 9-1-1 if you think you or someone else is having a heart attack.

Heart disease is the No. 1 cause of death in the United States. Heart disease is a collective term for various problems. Many types of heart disease are related to plaque buildup in the walls of the arteries, or atherosclerosis. As the plaque builds up, the arteries narrow, making it more difficult for blood to flow and creating a risk for heart attack and stroke. Other types of heart disease include heart failure, an irregular heartbeat – or arrhythmia – and heart valve problems.

Also called congestive heart failure, heart failure is when the heart can't pump enough blood to the organs. The heart works, but not as well as it should. Heart failure is almost always a chronic, long-term condition. The older you are, the more common heart failure becomes. Your risk also rises if you are overweight, diabetic, smoke, abuse alcohol or use cocaine. When a heart begins to fail, fluid can pool in the body; this manifests as swelling (edema), usually in the lower legs and ankles. Fluid also may collect in the lungs, causing shortness of breath.

The stages of heart failure is a rating system to evaluate the development and progression of heart failure symptoms. Developed by the American Heart Association and American College of Cardiology in 2001, the system includes four stages.

Stages A and B represent people who have not yet developed heart failure but are at high risk because of coronary artery disease, high blood pressure, diabetes or other predisposing conditions.

Stage C includes patients with past or current symptoms of heart failure who have a condition called structural heart disease.

Stage D includes patients who have advanced heart failure that is difficult to manage with standard treatment.

A heart-healthy diet is an important tool in preventing heart disease and stroke. The American Heart Association recommends a balanced diet that includes plenty of fruits and vegetables, lean meats and low-fat dairy, whole grains, and fish rich in omega fatty acids. A heart-healthy diet should limit saturated fat, sugar-sweetened beverages and keep sodium to less than 1,500 milligrams a day.

A heart murmur may be an abnormal, extra sound during the heartbeat cycle made by blood moving through the heart and its valves. Heart murmurs may be caused by defective heart valves. Murmurs also can be caused by conditions such as pregnancy, fever, anemia or thyrotoxicosis (a diseased condition resulting from an overactive thyroid gland). Innocent heart murmurs are sounds made by the blood circulating through the heart's chambers and valves or through blood vessels near the heart. Sometimes called functional or physiologic murmurs, Innocent murmurs are common in children and are harmless.

Heart rate (or pulse) is the number of times your heart beats per minute. Normal heart rate varies from person to person and is normally 60 to 100 times a minute. The best places to find your pulse are the wrists, the inside of your elbow, the side of your neck and the top of the foot. To get the most accurate reading, put your finger over your pulse and count the number of beats in 60 seconds.

Often referred to as a coronary calcium scan, a heart scan is a test used in the critical care setting to diagnose cardiac abnormalities. A heart scan provides a score to determine the risk of a coronary event and to diagnose coronary artery disease. Two machines can be used _ an electron beam computed tomography and multidetector computed tomography _ to make precise pictures of the heart using an X-ray.

A heart valve controls the direction of blood flow through the heart by opening and closing with each heartbeat. The four valves in the heart are the tricuspid valve, pulmonary valve, mitral valve and aortic valve.

Heart valve replacement surgery is an open-heart surgery to replace a defective or diseased heart valve. Natural replacement heart valves come from human donors and artificial ones are made of metal. In some cases, the procedure may use modified natural valves from animal donors.

A hemorrhagic stroke, also called a brain or cerebral hemorrhage, occurs when a blood vessel or an aneurysm bursts in the brain, causing bleeding inside the brain. Hemorrhagic stroke can also be caused by a head injury. It is different from a subarachnoid hemorrhage, which occurs when a blood vessel on the brain's surface ruptures and bleeds into the space between the brain and the skull.

Diastolic – registered between heartbeats (when the heart rests and refills with blood)

Blood pressure is measured in a numerical reading of millimeters of mercury, abbreviated as mm Hg. Optimal blood pressure is less than 120/80 mm Hg. In general, the lower your blood pressure is, the better.

120–129 and less than 80 is considered elevated

130-139 systolic or 80-89 diastolic is stage 1 hypertension, or high blood pressure

140/90 or higher is stage 2 high blood pressure. This puts a person at a greater risk for heart attack, angina, stroke, kidney failure and peripheral artery disease.

High cholesterol is a condition where there is too much cholesterol in the blood. High cholesterol levels can be reduced through diet and lifestyle changes as well as lipid-lowering medication if necessary. Left untreated, high cholesterol can lead to heart disease, stroke and other cardiovascular diseases.

A Holter monitor, also called ambulatory electrocardiography, ambulatory ECG or ambulatory EKG, is a battery-operated, portable device that measures and tape-records the heart’s electrical activity continuously, usually for a period of 24 to 48 hours so that any irregular heart activity can be correlated with a person’s activity. The device uses electrodes or small conducting patches placed on the chest and attached to a small recording monitor that is carried in a pocket or in a small pouch worn around the neck.

Hyperglycemia is a condition when a person has increased levels of blood sugar and is usually the first sign of diabetes. It can result in diabetic ketoacidosis and coma if not treated on time and adequately.

Hyperlipidemia is a condition in which there are too many lipids (fats) in the blood. Hyperlipidemia is commonly associated with high cholesterol and may be reduced through regular physical activity and healthy eating.

Blood pressure is the pressure of the blood against the walls of the arteries. When that pressure is consistently above the normal range, it is considered hypertension, or high blood pressure. This increases the heart's workload, putting a person at a greater risk for heart attack, angina, stroke, kidney failure and peripheral artery disease.

Hyperthyroidism is an overly active thyroid gland. This can lead to an overload of thyroid hormones, which can then speed up the body's metabolism. Symptoms of hyperthyroidism include weight loss and a rapid heart rate.

Hypertriglyceridemia is a high level of triglycerides in the blood. A high triglyceride level combined with low HDL ("good") cholesterol or high LDL ("bad") cholesterol seems to speed up the gathering of plaque in the arteries. A normal triglyceride level is less than 150 mg/dL. Hypertriglyceridemia has been linked to coronary artery disease.

Hypertrophic cardiomyopathy is a condition in which the heart muscle becomes thick. This thickening decreases the amount of blood that can be pumped from the heart to the rest of the body. Hypertrophic cardiomyopathy is the most common genetic cardiovascular disease, affecting about 500,000 people in the United States.

Hypoglycemia is a low level of blood sugar. It can be dangerous because blood sugar is the major source of energy for the brain. Low blood sugar can cause brain damage, or even death in prolonged instances. Hypoglycemia is common among those having diabetes if they receive too much insulin or if they don't eat enough.

Hypoplastic left heart syndrome is a birth defect in which the left side of the heart is underdeveloped. If not treated within days or months of birth, it can be fatal. Hypoplastic left heart syndrome can be treated with a series of operations, or may require a heart transplant.

Hypotension is the medical term for low blood pressure. Optimal blood pressure is less than 120/80 (systolic pressure is 120 AND diastolic pressure is less than 80). Within certain limits, the lower your blood pressure reading is, the better. There is no specific number at which day-to-day blood pressure is considered too low as long as you are not experiencing symptoms of low blood pressure such as dizziness, fatigue and nausea. If you are experiencing these symptoms, you should contact your doctor to determine the cause.

*All health/medical information on this website has been reviewed and approved by the American Heart Association, based on scientific research and American Heart Association guidelines. Use this link for more information on our content editorial process.